.alpha.-Trifluoromethyl vinyl acetate (2-acetoxy-3,3,3-trifluoropropene) is disclosed and claimed in U.S. Pat. No. 3,444,150 as a novel compound and as a starting monomer for the preparation of homopolymers and copolymers having a variety of uses. Among the copolymers disclosed is vinyl acetate-trifluoromethyl vinyl acetate copolymer, which may be hydrolyzed to vinyl alcohol-.alpha.-trifluoromethylvinyl alcohol copolymer, useful in the preparation of photographic processing compositions, as disclosed in U.S. Pat. No. 3,362,822. The homopolymerization of .alpha.-trifluoromethyl vinyl acetate, its copolymerization with vinyl acetate and the properties of copolymers so produced and the polyols derived therefrom are further described by Haas, MacDonald and Chiklis in the Journal of Polymer Science Part A-1, Vol. 7, pp. 633-641 (1969).
Haas and Schuler, in the Journal of Polymer Science Part A, Vol. 2, pp. 1641-1645 (1964) describe the preparation of 3,3,3-trifluoro-2-acetoxypropene (.alpha.-trifluoromethyl vinyl acetate) by the dehydrobromination of 3-bromo-2-acetoxy-1,1,1-trifluoropropane prepared from 3-bromo-1,1,1-trifluoro-2-propanol.
In U.S. Pat. No. 3,444,150, the reaction of 1,1,1-trifluoroacetone with trifluoroacetic anhydride to produce .alpha.-trifluoroacetoxy-3,3,3-trifluoropropene is disclosed and is given as illustrative of the reaction of ##STR1## with acid chlorides or anhydrides, where X is hydrogen or halogen preferably fluorine or chlorine. However, the patentees state only that "some monomers" within the scope of their invention may be prepared by this method and the method is not taught or shown to be applicable to the production of .alpha.-trifluoromethyl vinyl acetate. Instead, the latter compound is disclosed as being produced by other methods, such as the reaction of 3-bromo-2-acetoxy-1,1,1-trifluoropropane with tributylamine or the reaction of 2-trifluoroacetoxy-3,3,3-trifluoropropene with acetic acid. The method specifically described in U.S. Pat. No. 3,444,150 for the preparation of 2-trifluoroacetoxy-3,3,3-trifluoropropene involves the reaction of 1,1,1-trifluoroacetone with trifluoroacetic anhydride in the presence of potassium acetate in a steel bomb at 100.degree. C. for 16 hours.
Sladkov and Petrov in the J. General Chemistry U.S.S.R., Vol. 24, p. 459 states that the enol acetate of acetaldehyde was obtained by heating the aldehyde with acetic anhydride in the presence of potassium acetate. This method used by Haas and Schuler, J. Polymer Science Part A, Vol. 2, pp. 1641 (1964) apparently failed to produce product when applied to trifluoroacetone. They state that they were unable to prepare .alpha.-trifluoromethyl vinyl acetate by reacting trifluoroacetone with isopropenyl acetate, vinyl acetate, acetic anhydride or acetyl chloride, "except perhaps in trace quantities," with the use of a variety of acidic and basic catalysts and conditions. It can be concluded that acetylation methods operable for acetaldehyde do not necessarily work for trifluoroacetone. Therefore the teaching of Sladkov and Petrov with respect to the use of an excess of pyridine in the acetylation of acetaldehyde would not lead to the conclusion that trifluoroacetone could be similarly acetylated.
It is an object of this invention to provide an improved method for the preparation of .alpha.-trifluoromethyl vinyl acetate.
Other objects of the invention will be apparent hereinafter.